<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Upload</title>
</head>
<body>
  
  <div>
    <input type="file" name="file" onchange="uploadFile(this);">
  </div>
  <div>
    <pre id="ret-content"></pre>
  </div>

  <script>
    function uploadFile(t) {
      if (t.files.length <= 0) return;

      let fm = new FormData();

      fm.append('image', t.files[0])

      fetch('/upload', {
        method: 'POST',
        body: fm
      })
      .then(res => {
        return res.text();
      })
      .then(text => {
        let d= document.getElementById('ret-content');
        d.innerHTML = `<img src="/image/${text}" `
                    + ` style="width:80%;height:auto;">`;
      });

    }
  </script>

</body>
</html>